Mirza Cokoja

Ruthenium Nanoparticles inside Porous [Zn4O(bdc)3] by Hydrogenolysis of Adsorbed [Ru(cod)(cot)]: A Solid-State Reference System for Surfactant-Stabilized Ruthenium Colloids

The gas-phase loading of [Zn4O(bdc)3] (MOF-5; bdc = 1,4-benzenedicarboxylate) with the volatile compound [Ru(cod)(cot)] (cod = 1,5-cyclooctadiene, cot = 1,3,5-cyclooctatriene) was followed by solid-state (13)C magic angle spinning (MAS) NMR spectroscopy. Subsequent hydrogenolysis of the adsorbed complex inside the porous structure of MOF-5 at 3 bar and 150 degrees C was performed, yielding ruthenium nanoparticles in a typical size range of 1.5-1.7 nm, embedded in the intact MOF-5 matrix, as confirmed by transmission electron microscopy (TEM), selected area electron diffraction (SAED), powder X-ray diffraction (PXRD), and X-ray absorption spectroscopy (XAS). The adsorption of CO molecules on the obtained Ru@MOF-5 nanocomposite was followed by IR spectroscopy. Solid-state (2)H NMR measurements indicated that MOF-5 was a stabilizing support with only weak interactions with the embedded particles, as deduced from the surprisingly high mobility of the surface Ru-D species in comparison to surfactant-stabilized colloidal Ru nanoparticles of similar sizes. Surprisingly, hydrogenolysis of the [Ru(cod)(cot)]3.5@MOF-5 inclusion compound at the milder condition of 25 degrees C does not lead to the quantitative formation of Ru nanoparticles. Instead, formation of a ruthenium-cyclooctadiene complex with the arene moiety of the bdc linkers of the framework takes place, as revealed by (13)C MAS NMR, PXRD, and TEM.

A colloidal ZnO/Cu nanocatalyst for methanol synthesis

Free-standing, ZnO surface decorated Cu nanoparticles of 1-3 nm size were obtained by sequential co-pyrolysis of [Cu(OCHMeCH2NMe2)2] and ZnEt2 in squalane in the absence of additional surfactants and proved to be highly active quasi homogeneous catalysts for methanol synthesis from CO and H2.

Nano-brass colloids: synthesis by co-hydrogenolysis of [CpCu(PMe3)] with [ZnCp*2] and investigation of the oxidation behaviour of α/β-CuZn nanoparticles

A novel, non-aqueous organometallic access to colloidal copper and copper/zinc (brass) nanoparticles is described. Hydrogenolysis of the precursor [CpCu(PMe3)] (1) in mesitylene at 150 °C and 3 bar H2 quantitatively gives elemental Cu. Analogously, a solution of [ZnCp*2] (2) reacts with H2 to give elemental Zn in 100% yield. Co-hydrogenolysis of 1 and 2 in exactly equimolar quantities selectively yields the intermetallic phase β-CuZn characterised by powder X-ray diffraction (PXRD). Deep red colloidal solutions of nano-Cu as well as red to violet colloids of nano-brass alloys (α/β-CuZn) are obtained by co-hydrogenolysis of 1 and 2 in the presence of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as surfactant. All samples of the general formula Cu1−xZnx (0.09 ≤ x ≤ 0.50) were characterised by means of elemental analysis, PXRD, transmission electron microscopy (TEM, EDX and SAED) and UV-Vis absorption spectroscopy. The presence and alloying of metallic Cu and Zn in the β-CuZn sample as a representative example of the series was confirmed by extended X-ray absorption fine structure spectroscopy (EXAFS). The oxidation behaviour of the nanoparticles was investigated by EXAFS, PXRD and UV-Vis spectroscopy indicating, that CuOx@Cu core–shell type particles were formed for pure copper particles, while in the case of brass particles preferential oxidation of the Zn component takes place, which results in core–shell particles of the type (ZnO)δ@Cu1−xZnx−δ.

Ligand properties of Cp*Ga: new examples of Mo–Ga and W–Ga complexes

The compounds [ fac -(Cp*Ga) 3 M(CO) 3 ] ( 1a , M=Mo: 1b , M=W) were synthesized by reaction of [ fac -(RCN) 3 M(CO) 3 ] (R=Me, Et) with Cp*Ga. The treatment of 1a with one equivalent of [ fac -(MeCN) 3 Mo(CO) 3 ] gives the dimeric cluster compound [Mo 2 (CO) 6 (μ 2 -(GaCp*)) 3 ] ( 2 ). Addition of Cp*Ga to the Lewis-acidic unsaturated metal centres of [CpM(CO) 2 ] 2 (M=Mo, W) yields the dimeric complexes [(OC) 2 (Cp)M(μ 2 -(η 1 -GaCp*))] 2 ( 3a : M=Mo, 3b : M=W). The new compounds 1 – 3 were characterized fully including single crystal X-ray diffraction studies.

Dual Site Lewis-Acid Metal-Organic Framework Catalysts for CO2 Fixation: Counteracting Effects of Node Connectivity, Defects and Linker Metalation

Three Zr‐oxo‐cluster node and porphyrin‐linker based MOFs, MOF‐525, PCN‐222 and PCN‐224 exhibiting different linker connectivities of 12, 8 and 6 and their porphyrin‐linker metalated analogues, were synthesized and tested as catalysts for CO2 fixation by using the cycloaddition of CO2 and propylene oxide to propylene carbonate as the test reaction. In general, the catalytic activity correlates with the connectivity of the Zr‐oxo nodes. The lowest connected PCN‐224 (6‐fold) exhibits a superior catalytic activity in this series, while higher connected PCN‐222 (8‐fold) and MOF‐525 (12‐fold) are less active. Interestingly, the catalytic activity of the higher connected MOFs significantly depends on defects. The (ideally) 12‐connected MOF‐525, however exhibiting 16% of missing linker defects, features a higher catalytic activity compared to the 8‐connected PCN‐222 with less defects. The overall catalytic activity is increased in dual site catalysts when the porphyrin linkers are metalated with Mn(III) and Zn(II) centers, which are acting as additional Lewis acid sites. Here, the metalated MOFs with higher connectivity exhibit the highest activity.

Insertion of organoindium carbenoids into rhodium halide bonds: revisiting a classic type of transition metal–group 13 metal bond formation

Insertion of the carbenoid group 13 metal species InCp* (Cp* = pentamethylcyclopentadienyl) and InC(SiMe3)3 into the Rh-Cl bonds of [[RhCp*Cl2]2] yields the new complexes [Cp*Rh(InCp*)3(Cl)2] 1 and [Cp*Rh(mu2-Cl)2(InC(SiMe3)3)3] 2, respectively, exhibiting novel cage-like intermetallic complexes with In-Cl-In bridges.